1. Field of the Invention
This invention relates generally to hand tools which transmit rotational torque in a clockwise or counterclockwise direction, and more particularly to a cam-action ratchet-type hand tool which transmits rotational torque in a clockwise or counterclockwise direction between a driving element and a resisting element or workpiece.
2. Brief Description of the Prior Art
Hand held ratcheting tools are known which are used in conjunction with various types of attachable sockets to engage and rotate nuts, bolts, screws and other types of fasteners used in the fields of construction and manufacturing. Most prior art ratcheting tools use a pawl and toothed ratchet wheel combination which engage to produce a rotational torque on a workpiece in a selected rotational direction. Because of the required mating and interlocking of the pawl with the toothed ratchet wheel in these ratcheting tools the amount of counter-rotation of the work handle to back up for subsequent forward rotation is determined by the size of the interlocking pieces.
In order to reduce the amount of counter-rotation to the pawl and wheel, the mating pieces must be decreased. This reduction in size leads to a weakening of wrench strength which is based solely on the strength of the mating pieces. This size reduction will increase the work space limits of the wrench because of less counter- rotation of the wrench handle, but it also decreases the rotational torque that can be transferred to the workpiece. To increase the strength of the wrench, which would allow a much higher torque load transferred to the rotated workpiece, the pawl and toothed wheel mating pieces must be enlarged.
However, the enlargement of the mating pawl and toothed wheel also increases the amount of counter-rotation of the wrench handle because the wrench handle must be moved a greater distance to achieve the engagement of the interlocking pieces. This increased movement limits the wrench usage in a tight work space.
There are several patents which disclose ratchet-type hand wrenches.
Anderson et al, U.S. Pat. No. 2,139,650 discloses a wrench having a roller clutch mechanism wherein the head has a series of recesses arranged about a cylindrical rotor with a pair of rod-like rollers vertically disposed in each recess. A pair of springs urge the rollers into locking engagement between the cylindrical portion of the rotor and the bottom of the respective recess. A series of pins are carried by a disk to disengage one roller of the pair of rollers and the disk is rotatably retained by a snap ring. Anderson et al does not teach wedge members having flat surfaces or the use of a curved surface on the wedge members to conform to the cylindrical surfaces of the torque transmitting member.
Dossier, U.S. Pat. No. 3,447,650 discloses a one-way friction clutch wherein the effect of centrifugal force is used to disengage the clutch when the speed of rotation exceeds a given value. The device has a central shaft surrounded by an outer sleeve with two ring segments disposed in the space between the shaft and the outer sleeve. The opposed ends of the ring segments are provided with raised surfaces. The outer sleeve has a pair of recesses 180.degree. apart with an angled camming surface at the rear of each recess. A flat wedge is disposed in each recess and has an angled rear surface corresponding to the angled surface of the recess which requires that one side of the wedge be narrower than the other. The inner facing surface of each wedge has an angled cut-out defining a pair of protruding branches which are angled and slidably bear upon flat surfaces of the raised surfaces at the end of the ring segments. A spring at one side of each wedge normally urges each wedge in a counterclockwise direction wherein the angled rear surfaces of the wedges ride on the camming surface of the recesses and urge the wedges inward which causes the angled surfaces of the branches of the wedges to ride downwardly on the flat surfaces at the end of the ring segments. This draws the ends of the ring segments together and draws the ring segments radially inward to normally engage the shaft while the outer sleeve rotates freely in one direction, but is prevented from rotation in the opposite direction. Upon the outer sleeve exceeding a given speed of revolution, the centrifugal force overcomes the pressure of the springs, the wedge moves up (outwardly) on the angled surface, and the ring segments move radially outward to engage the outer sleeve.
Simometta, U.S. Pat. No. 3,677,102 discloses a wrench having a driving element with a toothed bore and a resisting element rotatably disposed in the bore. A pawl member is movably disposed in a slot in the resisting element and has two toothed ends which alternately engage the toothed bore to impart torque in one direction. The pawl is held in its selected operating position by a spring biased ball.
Lee, U.S. Pat. No. 3,958,470 discloses a double acting ratchet wrench employing a cam actuated positive drive oscillatory pawl which is engageable by a slight movement of the wrench handle and held tightly engaged by hand pressure on the handle.
Solomon, U.S. Pat. No. 4,063,626 discloses a silent ratchet in which a friction brake ring engages a pawl with the ratchet teeth in an annular ring. The friction brake ring carries the pawl into toothed engagement when the handle of the wrench is rotated in the direction in which it is desired to rotate a workpiece and a spring within the ratchet returns the pawl to a position in which it is disengaged entirely when the pressure on the handle is released to prevent the teeth from clicking on the return stroke of the handle.
Chern, U.S. Pat. No. 4,873,898 discloses a wrench wherein the head has a cylindrical recess with a series of concave receptacles arranged about a cylindrical driving head piece and a series of rod-like posts vertically carried by a rotatable circular post plate which has a notch extending inwardly from its circumference. A lever switch is pivotally mounted on the wrench handle and has a protuberence which is received in the notch for rotating the post plate and posts between a clockwise and counterclockwise position to move the rod-like posts out of their receptacles and into engagement between the exterior of the cylindrical driving head piece and the cylindrical recess in the head.
Korty, U.S. Pat. No. 5,086,673 discloses a wrench having a cylindrical recess in the head with three inwardly extending projections which define three radially extending partitions surrounding a central spindle. A vertical roller is located in each partition with with a coil spring at each side. A retainer cover having extensions between each partition and one end of each coil spring is rotatably secured in the cylindrical recess by a split ring.
Swedish patent 43,991 discloses a "Bar Feed Attachment" wherein an inner cylindrical member having an outer cylindrical surface is secured to an axle and is driven by the back and forth movement of an arcuate ring segment having a U-shaped cross section which is mounted on the periphery of the inner cylindrical member. Clamp members are rotatably mounted on pins in the ring segment and each has a curved outer surface tangent to the inner periphery of the outer ring segment and an inward facing curved surface. Spacers slidably disposed between the outer periphery of the inner cylindrical member and the clamp members each have curved indentations on an outward facing side in which the inward facing curved surface of the adjacent clamp rolls, and an inward facing surface which is slidably received on the outer periphery of the inner cylindrical member. The radius of curvature of the curved indentations in the spacers is greater than the radius of curvature of the tangent curved surfaces of the clamps so that the clamps partially roll in the curved indentations. Stop bolts disposed on each side of the spacers limit their circumferential movement relative to the outer ring segment. Outer springs are mounted between the outer sides of the clamps and a rigid part of the outer ring segment and inner springs are mounted between the inner sides of the clamps and opposed slide members connected with the outer ring. segment. The slides are displaced by a cam disk. The outer convex curved surfaces of the clamps cooperate tangentially with the concave curved peripheral surface of the ring segment and the concave curved surfaces of the indentations of the spacers to press the curved surface of the spacers against the cylindrical surface of the inner cylindrical driven member. Thus, the torque is transmitted through the tangent curved surfaces of the clamp which acts as a roller. The curved surfaces of the clamps engage the concave curved surface of the outer ring segment and concave curved surface of the indentations in the spacers only at the single point of tangency, and hence there is only minimum surface area in contact to transmit torque to the inner cylindrical member.
The present invention is distinguished over the prior art in general, and these patents in particular by a cam-action ratchet-type wrench having a handle with a hand grip portion at one end and a generally cylindrical head portion at the opposite end. A cylindrical torque transmitting member is rotatably disposed within the head portion and has a socket connection portion extending outwardly from the head portion for connection to a socket for rotating a workpiece. A pair of cam wedge members are movably disposed in laterally opposed spaced relation within rectangular slots in the head portion and have inwardly facing curved surfaces. A direction selection disk is rotatably mounted in the head portion above the torque transmitting member and has a pin member disposed between the cam wedge members. A direction selection lever on the handle rotates the direction selection disk to selectively engage the pin with one of the pair of cam wedge members to move the curved surface of the engaged cam wedge member into and out of engagement with the cylindrical surface of the torque transmitting member. The cam wedge members can be moved from a locked position wherein the handle, the torque transmitting member, and head portion rotate together as a single unit in both a clockwise and counterclockwise direction to an engaged position wherein one cam wedge member is disengaged from the torque transmitting member and upon rotation of the handle, the opposed cam wedge member becomes wedged between the slot and the torque transmitting member to cause the handle, torque transmitting member, and head portion to rotate together as a single unit in one direction only while allowing free relative rotational movement in the opposite direction.